Vehicle spring suspension



Jan. 21, 1941. A. F. HICKMAN VEHICLE sr'nme susrznsxou 11 Sheets-Shqt 1 QriginaL Filed March 16, 193'? ATTORNEYS 21, 1941. 'A. F. HICKMAN 21.696

VEHICLE SPRING SUSPENSION Original Filed March 16, 1937 11 Sheets-Sheet 3 w; i V INVENTOR f??? W av ATTORNEYS Jan. 21, 1941. F, HICKMAN I vzaxcma sranm susnusrou Re. 21,696 I 11 Sheets-Sheet 4 Original Filed March 16, 193'? ATTORNEYS m 1941- A. F. HICKMAN VEHICLE SPRING SUSPENSION Original Filed'larch 16, 1937 ll Shee ts-Sheet 5 ATTORN EYS E INVENTO'R 7?" W JanQZl, 1941. HICKMAN Re. 21,696 Y VEHICLE SPRING SUSPENSION Original Filed March l6,

l1 Sheets-Sheet 6 INVENTOR ATTORNEYS Jan. 21, 1941. F, H|KMAN Re. 21,696

V-BHICLE SPRING SUSPENSION- 11 Sheets-Sheet 7 Original Filed march 16, 1937 INVENTOR R ATTORNEYS Jan. 21, 1941. H|KMAN 7 Re. 21,696

' VEHICLE SPRING SUSPENSION Original Filed March 16, 1937 ll Sheets-Sheet 8 ATTOR N EYS Jan. 21, 1941. F. HICKMAN VEHICLE SPRING SUSPENSION- I Original Filed March 16, 1937 ll Sheets-Sheet 1O kfi x \Q MQ My 7 fix. a5: 3

ATTORNEYS Jan. 21, 1941. A. .F. HICKMAN I VEHICLE SPRING susrnus ion- 11 Sheets-Sheet 11 Original Filed larch 16, 1937 EQ M 60 MN .R m QQN m K I I] III! I I d 8% g g Y m 1 8% g ti 5 g M W l IlllllIl/flllll Reissued 21, 1941 UNITED STATES PATENT OFFICE vnmout srnmo susrnnsros Original No..2,l98,616, dated April 30. 1940, Serial No. 181,193, March 1, 1837. Application for reissue November 15, 1940, Serial No. 365,818

21 Claims. (01.280-124) i This invention relates to a vehicle spring suspension, and more particularly to a type of spring suspension in which each axle is permitted to move against a geometric resilient resistance,

5 both laterally and longitudinally, relatively to the vehicle frame, both when the vehicle has a low percentage of load variation and also when it has a high percentage of load variation.

The objects of the invention are-- 1. To reduce lateral impacts from against either the frame or the springs on a vehicle having either a high or a low percentage of load variation. g

2. To provide a tandem axle spring suspension in which one or both of the tandem axles are self steering so that said tandem axles are automatically caused to travel parallel to each other when the vehicle is moving straight ahead.

3. To provide a tandem axle spring suspension in which onoor both of the tandem axles are self steering so that. when rounding a curve, said tandem axles are caused to assume such an angle relatively to each other as will enable a F pure rolling action to be attained and thereby reduce tire soul! and increase tire and gasoline mileage.

4. To accomplish all of the foregoing and, at the same time, permit a certain amount of rearward wheel movement whenever either wheel moves upwardly, and a corresponding certainamount of forward wheel movement whenever said wheel movesdownwardly.

5. To accomplish the foregoing whenever both wheels of an axle are either elevated or depressed. 6. To accomplish these results in ample measme without imposing undue end thrusts on the various pivotal connections which connect the axles to the frame.

7. To accomplish all of the foregoing results 4 even though the. necessary resilient force be obtained from a spring which acts in a single plane and has an arithmetic rate of resilient resistance.

, 8. To enable the outer eye of a laminated spring to be twisted to a small extent without being opposed by an undue amount of resistance by said spring and, at the same time, without necessitating any expensive ball and socket joint to take care of this twisting action.

9. To provide a leaf spring-which will provide a smooth geometric rate of resistance against fiexure and not be noisy in action.

10.10 provide a means .of so pporting a member of a spring suspensi t moderate amounts of load are supported a soft resilient force which acts against a portion of said mem-.

the axles ber remote from one of its'polnts of support and enabling heavier loads to be supported by an additional resilient force which acts closer to said point of support, so as to increase the effectivestrength of the combination at the time when 5 it is most needed. I

11. To provide a plastic resilient support for a member 012a spring suspension in which the main body of said resilient support is on that particular side of said member which receives the maximum amount of loading.

12. To provide a plastic resilient support for a member of a spring suspension in which all parts of said plastic support are given an equal opportunity to serve in the supporting of said member.

13. To provide a means of protecting a resilient shackle in a spring suspension from dust. and, at the same time, of lengthening the lubrication intervals of said shackle. I0

14. To provide a resilient shackle for a spring suspension in which very accurate assembly fitting may be obtained without necessitating expensive machine work on the parts and without involving any manufacturing'operations (such as bending) which by their very nature cannot result in a product of uniform dimension.

15. To provide a resilient shackle for a spring suspension in which the resistance of said shackle to flexure is of accurate geometric nature and 39 yet can be manufactured with the most generous and easily attained manufacturing tolerances;

16. To provide a dual-drive, tandem axle in which a heavy traction is obtained whenever it is needed, but in which power from one of the 35 driving axles may be cut of! whenever the traction requirements are small, and when, moreover, there would be an unnecessary loss of power and amount of wear if the wheels of both of the tandem axles were forced to attempt 'to- 4 maintain a constant synchronism between mselves and, if, at the same time, each f the wheels were forced to attempt to ntain a constant synchronism between itseIf and all of the other wheels and the particular part of the roadway over which that particular wheel is traveling.

17. To provide a tandem axle spring suspension in which each of the tandem axles may be resiliently supported by a leaf spring in such manner as to take care of a high percentage of load variation and yet be so arranged as to not impose excessive rotative torques or thrusts upon said spring.

- 18. To provide a tandem axle spring suspen- 21. To provide a spring suspension having a in which all of the metal is substanequally stressed, whereby the eifective life spring is lengthened because of not ima few of the leaves the major the fatigue m l To effect the result Just mentioned withliability of at any time overstressing any of metal of any of the spring leaves beyond the fatigue limit.

wherein:

In the accompanying drawings:

' Fig. 1 is a fragmentary top plan of a dual drive tandem axle form of my invention.

Fig. 2 is a vertical, longitudinal section thereof, taken on line 2-2, Fig. 1.

Fig. 8 is an enlarged, fragmentary, side elevationof the rear end of the semi-elliptic spring of Figs. 1 and 2.

Fig. 4 is an enlarged, vertical, transverse section thereof, taken on line 4-4, Fig. 3.

Fig. 5 is a rear elevation, with parts in section, of the construction of Figs. 1-4.

Figs. 6-8 are enlarged, fragmentary, vertical longitudinal sections, showing various modified means of connecting the cross shaft of Figs. 1-5 with the frame of the chassis.

Figs. 9-11 are enlarged, fragmentary, vertical, transverse sections, showing additional modified means of connecting the cross shaft of Figs. 1-5 with the frame of the chassis.

Fig. 12 is an enlarged vertical, longitudinal section through one of the resilient shackles of Figs. 1-5, taken on line l2-l2, Fig. 13.

Figs. 13 and 14 are vertical, longitudinal sections through said resilient shackle taken on line ll-IS and ll-ll of Figs. 12 and 13, respectively.

Figs. 15 and 16 are horizontal, transverse sections through said shackle taken on correspond ingly numbered lines of Fig. 13.

Fig. 17 is an enlarged, side elevation of a modifled form of resilient shackle.

Fig. 18 is a vertical, longitudinal section thereof, taken on line lI-ll, Fig. 17.

Fig. 19 is a considerably enlarged, horizontal, section through still another modified form of resilient shackle.

Fig. 20 is-a fragmentary top plan of a tandem .oneofthe axles axle provided with my invention but having only power driven and, furthermore, having the semi-elliptic leaf springs mounted on a crank shaft.

Fig. 21 is a vertical, longitudinal section thereof, taken on line 2l-2l, Fig. 20.

Fig. 22 is an enlarged, horizontal section through the upper end of the torque arm shackle of Figs. 20 and 21, taken on line 22-22, Fig. 21.

Fig. 23 is an enlarged. vertical, transverse section through the vehicle frame showing the means of adjusting the tension in the transferring, torsion bar of Figs. 20, 21, taken on line 22-22, Fig. 20.

Fig. 24 is a fragmentary, top plan of a tandem axle spring suspension having a modified means of resiliently restraining rotation of its crank shaft.

Fig. 25 is a fragmentary, side elevation thereof.

Fig. 26 is a vertical, transverse section through the crank shaft and associated parts of Figs. 24 and 25, taken on line 28-28, Fig. 24.

Fig. 27 is a vertical, longitudinal section through said crank shaft and associated parts, taken on line 21-21, Fig. 25.

Fig. 28 is a fragmentary, vertical, longitudinal section through the rear end of a two-axle truck equipped with my invention.

Fig. 29 is a fragmentary, vertical, longitudinal section through the crank shaft thereof, taken on line 28-29, Fig. 28. A

Fig. 30 is a fragmentary, top plan of a two axle truck equipped wit a modified-form of my invention. f

Fig. 31 is a. vertical, longitudinal section thereof, taken online 3 l3l, Fig. 30.

Fig. 32 is a fragmentary rear elevation thereof,

2 .32, Fig. 31. Fig. is: ditic end elevation of a modified form of semi-elliptic, leaf spring.

Fig. 34 is a. fragmentary, top .plan of a two axle truck equipped with another modified form of my invention.

- Fig. 35 is a fragmentary, end elevation thereof.

Fig. 36 is vertical, longitudinal section through the rear end of a tow axle truck equipped with still another modified-form of my invention.

Fig. 37 is a. fragmentary, end elevation thereof.

Fig. 38 as. fragmentary, top plan of a two axle truck equipped with still another modified form of my invention. r

Fig. 39 is a fragmentary end elevation thereof, taken on line 39-38, Fig. 38.

Figs. 40 and 41 illustrate how rubber may be used in the present invention in place of or in addition to the metallic, resilient shackles of the previous figures, whereby to permit a. limited amount of longitudinal axle movement so as to allow the vehicle wheels to travel at a constant peripheral speed over a rough road without Jerking the frame back and forth.

Fig. 42 is a fragmentary and substantially vertical section through the. axle pivot and crank arm pivots of a vehicle and illustrates a construction similar to M 40 in that longitudinal cushionlng is eflected, in Race of or in addition to the flexible shackles of Figs. 1-39, by permitting the axle post to slide longitudinally relatively to the shackles, this sliding being resisted by an adjustable resilient resistance which in this case consists of helical springs.

tudinal cushioning wherever this is desired for reasons of economy of production or otherwise.

Similar characters of reference indicate like confining our attention for the present to I'jlgs. 1-19, the vehicle chassis consists of the usual rectangular frame ill consisting of a pair of longitudinal frame bars ll, Ill suitably joined together transversely by a plurality of cross frame bars I in the usual and well known'manner. Frequently, in modern practice, the imposed loads are transmitted directly from the vehicle spring suspension to the body in which case the "frame is little more than a template, but this question is of noimportance here and need only be mentioned in passing to prevent any impression that the present invention requires such a relatively heavy frame as that shown.

Secured by rivets 49 or otherwise to the inner face of each frame bar is a pair of downwardly projecting front, bifurcated brackets 53, "a (see Fig. 5) Arranged on said frame bar rearwardly of said front brackets are a pair of similar, downwardly projecting, rear, bifurcated brackets 54, a These rear brackets are longitudinally ad- Justable, relatively to their companion frame bar II or Sll, by means of adjusting screws 55, a

which are threaded in suitable angle plates 56,

56a secured to inner vertical faces of the web of their companion frame bar. when the proper adJustment of these rear brackets 54, "a has been suitably effected, the same are locked in position by fore and aft pairs of clamping bolts ll, Ila, it being understood that the holes in either the frame bars ll, ill or the holes in the rear'brackets themselves are either of elongated shape or are drilled sui'iiciently large to permit a small amount of longitudinal movement of said rear brackets relatively-to their companion frame The front brackets 51, Ila are connected to the front driving axle 58 in a manner identical with the connection between the rear brackets l, "a

and the rear driving axle ill and hence only the former connection will be described.

Plvoted at its inner bifurcated ends at M, In to-the front brackets 53, 53a is a Y-shaped lever 2. The axis of said pivots Si, is slopes downwardly and rearwardly, i. e., it is inclined to the horizontal but lies in a plane parallel to a vertical plane longitudinally through the vehicle. Each of said Y levers i2 is pivoted at its outer end on lower pivots C3 to the lower ends of a pair of resilient shackles M, a which will be subsequently described in detail. These shackles slope upwardlyan'd rearwardly from said lower pivots CI, as shown in Fig. 2, and also slope upwardly and inwardly from said pivots I, as shown in Fig. 5, and are pivotally connected at their upperendsattitoan axlepost" connectedwitha companion front driving axle is. This upward and inward inclined arrangement of said shackles tendstocauseeachaxletocentralize itselfina directiontransverse of the frame and enables the nnt'lnn nf navitv t0 eometrically and resilien y resist any such movement of said axle away from its ,central position. This permits the vehicle body to move substantially straight ahead despite a certain amount of lateral movement of the axle. This is what I term the "lateral cushion ing" of the vehicle frame relatively to one or more of the axles and is discussed at greater length in my earlier patents and patent applications. The novelty in the present construction doesfnot lie in this "lateral cushioning." per se, but in the application of this very desirable type of cushioning to any end of a vehicle which has a high percentage of load variation, as will appear more clearly hereafter.

The oblique position of the axis of the pivots I, "a permits either wheel 68 to freely move a short distance, rearwardly whenever said wheel rises and, concomitantly, permits said wheel to move a short distance forwardly whenever said wheel falls. This enables the peripheral speed of the wheel to be maintained substantially constant when travelling over irregularities, and, at

the same time, enables the axis of the wheel to receive the sudden horizontal thrusts which inevitably result as a consequence of said uniform peripheral speed, without imparting these thrusts directly to the frame. Some of these forward and backward thrusts are imposed upon the axle before its inertia enables it to rise rearwardiy or fall forwardly and these longitudinal thrusts are absorbed in the present invention by the shackles 84, a which are so constructed as to be resilient and thereby permit a limited amount of horizontal, longitudinal axle movement even in the absence of vertical movement of the axle such as occurs in practice when the irregularity is entirely absorbed-by the tire.

The axes at the upper and lower ends of the shackles are also disposed at an acute angle with respect to a vertical plane positioned transversely of the vehicle. This angularity, in combination with the upward, inward slope of the shackles, renders each of the rear axles inde- .pendently self steering, as will be explained hereinafter.

Pivoted horizontally and longitudinally of the vehicle at 69 at the outer lower part of each lever 02 is a rocking head ill provided with a downwardly proiectmg arm. The latter is pivoted horizontally an ,transversely at H to the upper end of a link 2 whose lower end, in turn, is horizontally and t ansversely pivoted at 13 to the companion end of a companion, semi-elliptic, laminated or leaf spring It.

The'central, thick part of said semi-elliptic spring I4 is pivoted on a cross shaft 15 which is iournaled horizontally and transversely of the vehicle in rubber cushions 16 arranged in companion cushion brackets I1, I10. It is to be understood that the cross shaft 15 does not rotate to any appreciable extent in these cushion brackets I1, 110, but only that the rubber cushions which are arranged between said brackets-I1,

"II and said cross shaft 15 permit the latter to flex freely without any metallic, positive hinderance and thereby permit such frame weaving as is bound to occur in actual practice, particularly in heavy trucks. These rubber cushions 16 also deaden such noises as would occur if the two metallic members involved were in direct contact with each other and were, in addition, able to move relatively to each other. It is true that the present invention employs the form of laminated cross bar 80 which has been explained in detail in my patent application Serial N0.

696303. flied Nov. 6, 1933, for Vehicle spring suspension. but it h to be remembered that this cross bar ll only controls the distance between the cushion brackets ll, Ill and not their angular position relatively to each other.

Obviously any increase in upward pressure upon the cross shaft of Fig. 5 imposes an increase in pressure on the rubber cushions l6.

- This pressure may, if desired, be resisted geometrically by the modifled type of rubber cushion showninl 'igo. Inthiscaseeachcushioncom 'sists of-three rubber rings lid, lib and 16c, all 7 of which have their outer peripheries arranged within a companion cushion bracket I'll but have bores of different diameter and are preferably constructed of rubber, or other plastic composition, of different hardness, as indicated. Ihe innermost or primary ring "a is constructed of the softest rubber and engages at all times with the adjacent part of the cross shaft Ill. As the vertical pressure imposed upon said cross shaft increases in an upward or downward direction, or in a rearward or forward direction, either one or both ends of said cross shaft "I are allowed to be deflected, substantially arithmetically, against said primary soft ring "a until the movement is sumclently large to cause said cross shaft 'lil to make contact with the rubber ring 18b which is preferably, though not necessarily, constructed. as shown, of harder rubber than the primary ring 16s. This secondaryringisnowabletoaidinlateral movement of said croa shaft III and hence, in combination with said primary ring 16a, is able to provide a more or less geometric resilient resistance to lateral movement of said cross shaft iii. In a similar manner, a still greater lateral pressure imposed upon said cross shaft ISI causes a still further lateral movement of said cros shaft until it makes contact with the large-bored and preferably hard rubber, outermost rubber ring 18c. It is to be noted that when the heaviest pressures are exerted upon said cross shaft "I. the point of support, relatively to the vehicle frame, is nearest its outboard end where the p w: are .being received from the companion semi-elliptic spring In Figs. 7 and 8 are shown other modified means of providing a geometric, resistant, rubber connection between a cross shaft and its companion vehicle frame. In Fig. 7 is shown a pair of rubber rings lid, lie both'of which arealways in contact with their companion cross shaft II! but provide a geometric resistance because of the fact that the inner ring lid is constructed of relatively soft rubber while the outer ring lie is constructed of relatively hard rubber. In Fig. 8 is shown a construction in which only isemployedbutinwhichtheborethereofis tapered so that,.as the load on the cross shaft It! increases, the point of support moves outwardly and the resistance incr. 'Ihe bore shown in therubberringofthisFlg.8isataperedborein which the taper is straight, but it is obvious that thistapermaybesoconstructedastobeofcurvilinearshapeifitisdesiredtosecurearesilient resistance having a different geometric characteristic.

Figs. 9-11 illustrate other modified forms of the invention wherein rubber cushions are used to maximum effective economical advantage. In Fig.9eachendofthecrossshaftl54isnormally eccentrically with respect to the cushion bracket lllsothatthebulkoftheeocentricrubberrlnglimwhichisinterposedbetweensaidcross a single rubber ring 16;-

shaft and said bracket, is located above said cross shaft so as to provide the maximum amount of rubber where its presence is most necessary. Similarly, in Fig. 10 a pair of rubber blocks 1th is disposed between horizontal flanges II, which are suitably secured to the cross shaft I55, and a pair of horizontal flanges 82 which are suitably secured to the vehicle frame. In this particular construction it is preferred that the rubber blocks be securely cemented to the metallic surfaces with which they make contact, so as to properly take care of both horizontal forces and downwardly directed forces. In the previous constructions of Figs. 5-9, such a cementing renders the action of the rubber cushions more positive but is not ordinarily necessary for the preventing of relative movements of rubber and the metallic surfaces with which they make contact.

Fig. 11 is a construction similar to Fig. 10 except that heavy downward movements of the cross shaft 156 are resisted by compression of an additional pair of rubber cushions 161' instead of relying upon the tensile strength of the upper rubber blocks Iii as in Fig. 10. This construction of Fig. 11 is particularly adapted for use where trucks are to be driven at very high speeds over a very rough road or terrain as occurs, for instance, when trucks are used for army service.

As shown in Fig. 2, the lower eight leaves It .of the semi-elliptic spring 14 are all very thin and are of equal thickness. The upper leaves ll of said spring are, on the other,hand, relatively thick and are also of equal thickness, but this thickness is larger than Furthermore, the. upper, thick spring leaves 84 are relatively straight whereas the lower thin leaves are all provided with a certain amount of camber. The action of such a "compound," semielliptic spring is to provide a geometric rate of resistance in which the resistances to initial movement are progressively greater but very small in amount whereas resistances to increasing movement are progressively greater and relatively large in amount. In addition to this the construction of this leaf spring 14 is such that the normal life of all of its leaves is'the same. This result is obtained by so proportioning the size and the shape of the lower leaves 83 as to have a proper fatigue strength based upon the very high total number of stress fluctuations to which they are subjected during their total life. The upper, thick leaves 84 are also so proportioned as to have a proper fatigue strength based on their total number of stress fluctuations but this latter-number is relatively so low that these upper spring leaves may be considered as subjected to merely static loads and hence the allowable stress may be much higher than with the thin leaves 83.'

As far as pure stress in the different leaves is concerned, such a differential in stress could be obtained by relatively minor changes in a conventional laminated spring. But another factor is involved, namely that the spring provides a geometric rate of resilient resistance with avery "flat" curve at normal loadings and a very rapid change to a "steep" curve at higher loadings. Applicant's spring attains both of these results simultaneously by having each infinitesimal portion of steel in each spring leaf stressed in accordance .with its particular fatigue strength as encountered in. actual service and, at the same time, by having the spring so arranged, as a unitary whole, as to be very soft for increments of load slightly greater than its normal load and the thickness of the lower leaves 83.

rapidly, increasingly stii! tor increments load difierent from its normal load. Whsnoneendonlyoi'eitherthemaindriving axleilorthetrailingdriving axlel|israised orloweredacertainamountofundesirabletwisting strain is imposed upon the semi-elliptic spring. and the latter naturally opposes a twisting movement and thus renders the spring suspension unnecessarily still. as to this particular movement. Figs. 3 and 4 illustrate how applicant has arranged the present invention as to reducesuchtwlstingstrainsonthespringleaves as a consequence of such an axle movement and has, concomitantly, enabled one or both of said axles to move more very freely and wily under such conditions. Applicant has obtained this effect by taper grinding the outer undersides I. of that particular lowermost spring leaf "a which is not connected to the pivots II at the lower ends of the links It. Thus the two lower thin leaves "b which are connected directly to the lower ends of the links 12 are thus enabled to twist slightly. when the one end only of either axle rises or tails, without requiring that the spring leaf 83a and all of the spring leaves above the same be also twisted or tilted. This taper grinding of the third-from-the-bottom spring leaf Ila does not material y aiIect its strength or fiexure characteristics because said grinding causes the outer ends of said leaf to be of substantially. equal-strength, cantilever form. In other words, this removal of metal at the ends of said spring leaf 83a has no material efiect on its resilience or its stress characteristics and only an insignificant effect on its inertia and momentum, but does enable the leaf spring as a whole to be more easily twisted.

The resilient shackles 64, a. may be constructed as shown in Figs. 12-16 as iollows:

Securely clamped to the axle pivot 85 by a clamping nut 81 is a pair of heavy-gauge, sheet metal, upper shackle heads 88. Similarly clamped to the crank arm pivot 63 by a clamping nut 9|! is a similar pair of lower shackle heads OI. Clamped between said upper and lower pairs of shackle heads 88, 8i and secured thereto by rivets 92, are two sets of laminated, metal, resilient strips 93 which carry the tensile stress to move longitudinally relatively to each other and to swing a small amount out of parallelism relatively to each other whenever their companion axle rises or falls, this movement being due to the fact that the pivots 65, 83 are not parallel to the frame pivot or fulcrum 6|, Ola of the Y-shaped lever 62. These laminated strips 93, being resilient, permit the pivots 85 and 63 to move a short distance longitudinally relatively to each other and also to twist slightly relatively to each other as just explained. Resistance to both of these movements should be.and in the present invention is, of a geometric nature, as explained in detail in .my pending application for Vehicle suspension,

Serial N0. 85,726, filed June 17, 1936. This geof the laminated strips 93 by curvilinear faces 04 formed on the upper and lower shackle heads UI and 8|. To obtain such curvilinear faces 94 by a machining operation is expensive, and die casting is, of course, out of the question. On the other hand, while these heads are made of heavy sheet metal and can be bent to shape, it is well known that the product of such bending is sure to be variable in actual production practice. In

between the pivots 65 and 63 and allow the latter ometric eiiect is obtained by limiting-the flexing the present invention all of these diillculties have beensurmountedbynrstbendingsaidheads ll, 0| a relatively small amoimt and then assembling and-clamping them together (with the laminated strips l2, etc.. in place). with a small spacing pin Ii interposed between each pair oi heads, said pin being received at its opposite ends in shallow, cylindrical depressions ll suitably iormed in the opposing faces of each pair of heads. Both the length of these pins 0 and the depth of the impressions N can be easily machined within close tolerance limits and hence as. Said wick I1 is saturated with lubricating oil or light grease when the shackle is assembled at the factory and this has been found, in actual practice, to efl'ectively lubricate the laminated strips 83 for a verylong period of service and prevents said strips from rusting while in service and also prevents dust from working into the interior of theshackle. 1 I

It will be noted in Figs. 1 and 2 that-the resilient strips 93 are shown as normally disposed in a plane which is perpendicular of the axes of the pivots and 63. To eiIect such a result it is, of course, necessary to so form the resilient strips 93 that they have an initial curvature prior to being installed in the vehicle. This is deemed duces the end thrusts on said pivots 6i and 63 but the present invention is not confined to such a normally perpendicular positioning of the shackles because, particularly in light and/or inexpensive vehicles, the resilient strips 93 may be normally arranged in a plane which is vertical and disposed transversely of the vehicle. In such case the shackles may be manufactured symto be the preferred arrangement in that it remetrically without providing any initial fiexure.

in the resilient strips 93. 7

Figs. 17 and 18 illustrate a modified form of shackle in which the shackle heads 88]: and Oils have straight inner faces, the geometric feature of the resilient resistance of the shackle being obtained by the arrangement of the laminated strips themselves. In this case the laminated strips are of variable length, the central five strips 98 extending the full length of the shackle, while the outer strips III are progressively shorter in length. All of the strips are suitably secured at their outer ends to the shackle heads 88k, 9H0 by rivets 921:. Thus, despite the fact that all of the strips are of equal thickness, whenever the shackle is increasingly flexed, the inner fiat faces 84]: of the heads-88k and elk make abutting contact,with the tips of the successively longer strips 100 and thereby cause the shackle as a whole to resist fiexure at an accel-\ shackle does not need any spacing pins 95]: at all, but to obtain compactness itis desirable to have the strips as short as possible and this result in-=.

the outermost strip llillk of the graduated strips =1 I00 being so short as to not secure a solid: base of a support for the nuts 81k and k and thereby tending to thrust the outboard ends of each pair of shackle heads "I: and ill: toward each other. Any'such tendency is prevented positively and accurately by the aforesaid spacing pins ilk.

If desired a felt block or lubricating wick l'lk all of the resilient strips and hence are able to prevent any possibility of the graduated strips Ill moving inwardly toward each other and interfe'ring with the lubricating felt 91.

15 mg. 19 shows a modified form of resilient shackle which is similar to the form of Figs. l7,

18 except that, instead of all of the resilient strips being of equal thickness, the central resilient strim Ill are relatively thick while the outer resilient strips III are progressively thinner.

This arrangement equaliaes the effective stress in the various strips either if we assume that the increase in length ofthe strips is subtantially arithmetic as indicated in the con- 25 struction of Figs. 17 and is, or if we assume that the e increase in length is of geometric character. This equalization of the effective stress results from the fact that the number of vibrations to which the outer strips are subjected 30 during the total life span of the shackle is considerably reater than the number of vibrations to which the inner strips are subjected. This is because every movement of the shackle causes a relatively sharp flexing of the outer strips whereas only the larger movements of the shackle cause any sharp bending of the inner strips. It is well known that a thin strip can be bent around a given radius with less maximum stress imposed upon the outer fibers than in the case of a thicker 4o strip. Hence, even if the actual radius of curvature is the same for both the outer and inner strips, the static stress on the thinner outer strips is less and, because of their larger total number of vibrations per life is greater, the effective stress iscaused to be the same in all the strips of the shackle. In other words, this shackle is like the one horse shay in that, when any one strip reaches the end of its life and breaks,'all of the other strips have also reached the end of 50 their lives too. This is, of course, a theoretical ideal and cannot be strictly obtained in actual commercial practice, but it is the ideal to be sought and forms the proper basis for the design of the various parts of the shackle.

55 A tandem axle arranged at the rear of a truck and in which both of the tandem axles are power driven unquestionably provides a superior traction inasmuch as all of the wheels at the rear end of the truck are driving wheels, and hence so the full weight imposed upon the rear end of the truck is utilized in obtaining traction. n the other hand, after the truck has been brought up to a relatively high speed and the inertia of the vehicle has been overcome any such dual cs axle traction is not only unnecessary in the driving of the car at the desired rate of speed, but is extremely detrimental in that it tends to cause all of the rear wheels to travel at a constant rotative speed even though their natural incli- 7 nation is to each travel at a speed which accords with the particular terrain being traversed by that particular wheel.

In the present invention applicant has so organiaedthevariouspartsthatatlowspeedsboth 75 of the rear axles are caused to provide their full driving function but that at high speeds the power is unconnected from one of the erstwhile drive axles. Fig. 1 shows the front axle 68 provided with a conventional front diiferential 'lol and the rear axle OI provided with a conventional rear differential I03. The front axle it is at all times connected to the usual and well known ton gear box of the vehicle through the conventional propeller shaft I and the rear,

main universal joint I II. The rear axle on may 10 receive its power in any suitable manner, as for instance, from the front diiferential Ill! through a pair of universal Joints I06, I01 and a splined drive shaft ill. The rear differential I3 is pro- -vided with a clutch lever no which is adapted,

by a suitable clutch (not shown), to couple or uncouple the power from said drive shaft ill! to said rear diflerentiai I". Thisclutch lever HII is connected to the transmission of the vehicle by an actuating rod III in such manner that whenever said transmission is in the lower range of gears (for instance first or second gears) said clutch lever III is automatically actuated to engage the clutch in the rear differential I03, whereas, when the transmission is in the higher range of gears (for instance third or overdrive gears) said clutch lever III is automatically actuated to disengage said clutch in the rear differential I 03. It isto be understood, of course, that. when the transmission is in reverse gear,

' power is delivered to both of the rear axles.

It is, of course, quite possible to couple and uncouple the one or other of the tandem axles by some suitable manual apparatus and the latter is deemed to come within the scope of the present. invention. It is well known, however, that the human element should never berelied upon if itcan be replaced by some automatic apparatus or other. The present invention is ideal in this respect in that when the truck driver 40 throws in first gear, the power is automatically caused to be delivered to both of the tandem rear axles i8, 60 through their respective differentials. Such an arrangement may, if desired, be continued when he throws in second gear. But in any event, as soon as the truck has sumciently overcome its initial inertia to warrant shifting of the gear shift to a relatively high gear, for instance. third gear, the uncoupling of the rear axle I is automatically effected by this shift withoutany mental effort on the part of the truck driver. If the truck is being used to pulf some object which is very heavy. such as'a cement izixer, the truck driver will automaticallybe fare to stay in low or second gear and power will automatically be supplied to both rear axles and full traction thereby obtained. The same general condition obtains if the truck, either empty or loaded, strikes a hill which is suflloiently steep to require one of the lower gears. When the truck driver throws his gear shift into neutral and comes to a stop or if he materially reduces his speed and has to drop into a'lower gear to pick up speed again, power will automatically be delivered to both of the tandem axles. It is obvious that the present invention in no way prevents any wheel from being equipped with a brake, so that, despite the fact that the traction is reduced at high speeds as far as propulsion is concerned, it is not reduced one iota as far as braking is concerned.

It is to be-noted, in this form of the invention, that the starting and brake torque of the tandem axles is not transferred to the semi-elliptic springs 14 but is carried directly through the vehicle.

. follows:

-loadsonlyanddnothavetobemadeheavy enough to carry momentary torque loads and hence do not have to be made so heavy as to interfere with their resilient characteristics in normal operation. It is also of great significance in the present invention that said semi-elliptic sprins ,are not forced to carry any transverse loads which in actual practice are very heavy, and are imposed upon only those leaves of the ordinary, semi-elliptic spring suspension which areconnected tothe spring eyes 18. Also it is because of the fact that, in the present invention, the semi-elliptic springs ll only carry the vertical loads, that their central bearings on the cross shaft OI may be constructed very light and the cross shaft itself very light and the latter mounted in such rubber cushions as those shown in Figs. -11, as would absolutely be unfeasible in a spring which is forced to carry torque and/or transverse loads. It is true that, in the present invention, the lowermost of the thin spring leaves 81 are subjected to twist, but this is only because of the arcuate movement of the pivot is about the fulcrums ii, Ma and this arcuate movement is very small and does not constitute a direct lateral thrust on said spring leaves and'the strains that are imposed are very considerably reduced by the tapered shape 86 of the third-from-thebottom leaf "a.

I The pivots 8i, Bio of the levers t2 incline to the horizontal, as previously described, to enable each wheel to move slightly rearwardly when it rises, and, conversely, to move slightly forwardly when it descends, so as to enable the horizontal component of the wheel axis movement to remain substantially constant, even though its peripheral speed is substantially constant but is travelling over a rough road.

In addition to this, the pivots 65 and 83 of the shackles M, a are inclined with respect to a vertical plane positioned transversely of the The reason for this angularity is as when the vehicle is travelling straight ahead, if the tandem axles 58, Cl are not parallel for any reason, they will automatically assume a parallel position because of the fact that any rear axle which is out of line will tend to follow a horizontal arc and this tendency, due to the lateral friction between the tires and the roadway, will cause a lateral movement of the axle relatively to the frame. Dueto the fact that the shackles normally extend upwardly and inwardly, as shown in Fig. 5 and due to the further aforesaid angularity of the shackle pivots with respect to a vertical, transverse plane, this lateral movement is automatically caused to be translated into a slight turning movement of the whole axle, and this turning movement will continue until both of the rear axles are in line with each other. Such a movement, naturally, causes a change in the angularity of the shackles at the opposite ends of each axle and this change is resisted by. gravity which, due to the obliquity of the shackles, is caused to act in a geometric manner. It is obvious that this self-steering movement should be as small as possible because of this gravitational resistance to lateral axle movement, and it is for this reason that the position of the rear axle in a horizontal plane is rendered adjustable by the adjusting screws 55, 55a and clamping bolts 51, 510 so as to reduce as much as possible the need for this self-steering.

the rear axle OI to be bly room at the time permits said axle to be brought back to if frame distortion has occurred in use, as is very frequently the The fact that the-rear axles 0, III trail" each other also occurs when the vehicleis making a turnontheroad. Inthiscase,justaswhen going straight ahead, the tires naturally tend to resist lateral scufling and tend to push the axle laterally and, as a consequence. the whole axle moves obliquely to eliminate this scuiiing. Thus when the vehicle is making a turn the two rear axles are caused to automatically move to such" an oblique pofltion, relatively to each other, as

wilic ausetheiraxestointersecttheaxes of revolution of the two-front wheels and will enable the vehicle to make the turn without tire scufling. This action occurs when either the vehicle is steeredaroundalongturnintheroadorifit is steered sharply on a straight road, as, for in stance, when overtaking a slow vehicle ahead, or otherwise avoiding some obstruction or other. It is to be understood that this action also takes place to some extent when a tendency to tire scufling occurs because of one wheel or a pair of wheels at one end of an axle having a diameter different from the diameter of the wheel or pair of wheels at the other end of the same axle.

V Figure: 20-23 In this tandem axle construction, the front axle 582 is driven by the propeller shaft I042 while the rear axle .02 is not power driven but is merely a trailing axle, this construction being particularly adapted for lighter and less expensive vehicles. Because all of the starting torque is imposed upon the drive axle "I, the latter is preferably (though not necessarily) provided with a conventional form of torque arm I I2 whose front end is connected to the lower end of a torque link 3. This eliminates the need of a special. stronger connection between the drive axle 582 *and the frame, than that used between the trailing axle Oil! and the frame. The upper end of the torque link III is pivoted at ill to the vehicle frame and, because of the fact that the drive axle must be free to tilt freely in a plane which is vertical and transverse of the vehicle,

the upper end of said torque link is connected through a resilient rubber or other similar connection II! to the main frame of the vehicle.

In this form of the invention is shown a modifled means of connecting the central part of the semi-elliptic spring III with the vehicle frame. Journaled horizontally-and transversely on the main frame Bill is a two-piece crank shaft IIG having crank pins III at its outer ends. Rotation of this crank shaft ii is resiliently restrained in any desired manner, for instance by the helical spring Ill which is connected at its front end at I" to the main frame of the vehicle and is connected at its rear end to a chain belt III which is wrapped around a smooth-faced, flanged segment III which is suitably secured to the crank shaft I.

Journaled intermediate its ends upon each of said crank pins ll'fiis a semi-elliptic, leaf spring crank pin may be either adJustably or fixedly located any desired distance forwardly of this central position so as to increase the proportion of load on the drive axle 582 as compared with not 50-50, as will be shortly explained.

It is obvious that the construction of Figs. 1-19 could be equipped with this crank shaft III, if desired.

The rear end of a truck is subjected to very heavy pressures, and these pressures are practically always laterally unbalanced when the truck is in motion. The percentage of the effective unbalance is usually rather low, particularly when the truck is heavily loaded and traveling at a relatively high speed, but nevertheless causes a tendency to tilt the rear end of the vehicle frame in a vertical transverse plane. If none of this tilting effect is transferred to the front end of the truck the result is that the entire truck frame is twisted, as is'weli known in actual practice. on the other hand, if a large portion of the resilient forces at the rear end of a truck were transferred to its front end, the effective force at the front would be the difference of the pressures at the rear end of the truck and this would cause the front end to heel over in the correct direction but altogether excessively in amount. Also the mechheavy and costly.

In the construction of Figs. -23 is shown a means whereby a sufficient portion of the forces which cause tilting at the rear end of the vehicle are transferred to the front end of the vehicle, so as to eliminate all twisting strains, as far as tilting forces originating at the rear end of the vehicle are concerned, by causing the frame to tilt an equal amount at the front and back ends. This means consists primarily of a pair of torsion rods I23 each of whose front ends is adjustably secured through a ratchet wheel I24 to the front end of the vehicle frame, while its rear end is secured to the companion, Y-shaped lever 622 of the front tandem axle or driving axle 582. Hence, as the one or other of said Y levers 62! moves up or down, this movement is translated into a torsional strain which is carried to the front end of the vehicle frame which latter is then tilted in the one or other direction in accordance with the tilt at the rear end of the vehicle. This eliminates any twisting frame stress as far as any tilting which may originate at the rear end of the vehicle is concerned. 7

The amount of the torsional strain thus transferred to the front end of the vehicle is, of course, a-function of the diameter, length and metal of the torsion rod and this is properly de igned to take care of such stresses as result from maximum loading. It is well known, however, that the variation of load on a truck is considerable, and hence provision has been made in the present invention whereby the amount of stress transferred may be adjusted if desired. This consists of a regulating handle I25 whose hub is journaled on the front end of its companion torsion rod I23 and carries the usual spring actuated dog II! which may be tripped in the usual manner by a trip lever III. A suitable pedal-actuated pawl I28 is also provided to'restrain the ratchet wheel I24 from rotating relatively to the vehicle frame, the same being-pivoted at I30 on the vehicle frame and having a treadle plate IlI at its inner end adapted to be depressed by the foot of the vehicle operator."

While the primary purpose of adjusting the effective torsion of the torsion rods III is to eliminate frame twisting. it should also be noted that in an emergency, the same may be used to impou a much heavier than usual downward force on the drive axle S82 and thereby supply the same with the required greater driving traction.

The use of torsion rods I20 lends itself particularly well to the construction of Figs. 20-23 in that it imposes an additional resilient pressure on the front axle "I and hence provides a load distribution which is not 50-50 even though the leaf springs I42 are constructed symmetrically with the crank pins II'I iournaled exactly midway of their ends. It is to be understood, however, that such a pair of torsion rods may also be used in the construction of Figs. 1-19, but as the load distribution in such a dual-drive, tandem axle construction is preferably always 50-50, it is preferredinthatcasethatthestraintowhich the torsion rods are subjected be derived from only the front axle but that the semi-elliptic spring be unsymmetrical to preserve the 50-50 load distribution.

Figures 24-27 The tandem axle construction of Figs. 24-27 shows a means of eliminating the helical spring III of Figs. 20-23. This result is obtained by employing a rubber sleeve I32 intermediate each end of the two-piece crank shaft Him and its companion frame bracket IIm. It is to be understood that, in the position of the parts shown in the drawings, each of the rubber sleeves is under torsional strain tending to turn the crank shaft in a counter-clockwise direction, as seen in Fig. 25, and hence resiliently resisting upward movement of the crank pins II'Im.

- To enable the resilient rubber sleeves I32 to be readily replaced after a certain period of use, each of the same is preferably cemented to an outer metal tube I03 and an inner metal tube I34, the latter being connected to the companion end of the crank shaft I Iim by a key I35, and the former being connected to its companion bracket I'Im by a key I". a

Figures 28-29 This modified form of the invention also employs a rubber sleeve I321: to resiliently restrain rotation of a transversely disposed, double-ended crank shaft in, but in this case only a single rear axle 58a is employed, the same being secured at each of its ends to the central part of a longitudinally disposed, semi-elliptic, leaf spring Iln. The one end of each of said leaf springs is pivoted at I to the vehicle frame while its other end is pivoted on the crank pin IIIn of the companion end of the transverse crank shaft in.

Figures 30-32 This modified form of the invention illustrates howthe lateral-cushioning constructions of Figs. 1-27 may be modified for use in a truck requiring only a single rear axle 580 and employing endsofresilientshacklesflowhoseuppcrends are pivoted at "0 to the drive axle Ito.

This form of the invention also illustrates how a leaf spring 140 may be constructed to provide a very smooth geometric, resilient resistance, by being constituted of three distinct sets I, Hi and I of spring leaves, the leaves in each set being of equal thickness, but the thickness of the leaves in each set being different from the thickness of the leaves of the other sets. I It is to be noted that this form of the invention I is similar to that of Figs. 1-19 in that the leaf spring 140 carries the vertical loads only and that the torque forces imposed upon the'axle are carried to the frame through the shackles o and levels 620 without requiring any special radius rods or wishbones" to effect this result. In addition this construction provides the lateral cushioning feature, namely that the axle is geometrically resiliently urged in a vertical, transverse plane, but is not positively held in this central position and that,

therefore, the axle may swing up and over at either one of its ends or may move bodily laterally a limited amount without being forced to move laterally with the body. It will also be noted that the axis of the pivots 030 and 850 are normally disposed at an angle to a horizontal plane and also at an angle to a vertical, longitudinal plane, thus causing the axle to automatically "trail accurately just as in the case of the tandem axles of Figs. 1-27. In the present instance, of course, we are only dealing with a single rear axle and in this case this trailing feature is not such a vital feature as in the case of the tandem axles. Nevertheless it is considered to be of value in even this case as it takes care automatically of inaccuracies of rear axle alignment on the frame and also any inaccuracies in the relationship of the front wheels to their steering linkage.

In addition to this, when the vehicle is rounding a curve or is otherwise subjected to heavy lateral forces, it reduces the tendency to'tire scuff by causing the axle to swing to a slight angle relatively'to the frame and to trail" outwardly so as to allow a certain amount of lateral body movement and thereby reduce the effect of the lateral force.

Figure 33 This figure discloses a modified form of semielliptic leaf spring in which all of the leaves I of the leaf spring are of equal length, and in which, furthermore, the maximum stress to which the different portions of the leaves are subjected is limited by so forming the lower face of the frame member I. as to provide a curvilinear, limiting abutment I45. The action of this abutment ill is similar to the action of the curvilinear faces 94 of the resilient shackle shown in Figs.

12-16, in that primary movements of the leaves a I cause said leaves to first make contact at a successive outward point starting close to theirpoint of support (the U bolt I) at which time the metal in the leaves at this point has been allowed to reach its maximum allowable stress and then restrained against further stress, and to then allow further spring flexure by allowing the successive outer parts of the spring to flex until they too have reached a maximum allowable stress and then prevented from being strained further.

The principal advantage of such a spring is that it permits of a very accurately controllable geometric rate of resilient resistance with an untoward a central position that those ,portions of the leaves which are subjected to the greater" number of vibrations throughout their entire life can be given a smaller 5 maximum stress.

Fwd! 34, 35

This construction illustrates how "lateral cushioning," self-steering and other advantages of the present invention may be obtained when helical springs are used as the resilient restraining means. In this case the levers 62a are relatively long and are pivoted to a bar I secured centra'lly and longitudinally of the vehicle frame on- 16 the two cross frame members I41, I.

- Resilient resistance to upward movement of each of the levers "q is obtained by the use of a pair of helical spring nests I", each nest consisting of an outer helical spring III and an inner helical spring I52, as shown in mg. 35. The inner spring IE2 is relatively short and does not come This construction is similar to that of Figs. 34, ,30 35 except that rubber springs I53 are used instead of helical springs. These rubber springs I53 also provide a geometric resilient resistance, but it is not deemed necessary to explain their action in detail more than to say that each rubber spring consists of three metal rings of different diameter and arranged one above the other and encasing a single core of rubber whose deformation is controlled by said rings.

'It will be noted in l 'ig.v 36 that the frame bar m, upon. which the levers'flr are fulcrumed, slopes rearwardly and downwardly so as to enable each of the vehicle wheels to move rearwardly when it rises and move forwardly when it descends so as to permit said wheel to maintain a uniform peripheral speed over rough ground without Jerking the frame back and forth. This is similar to the arrangement of the axis, of pivots ti, la in the construction of Figs. 1-19. In a similar manner, also, the shackles 641- slcpe upwardly and inwardly to provide lateral cushioning and also slope upwardly and rearwardly which latter characteristic, in combination with the upward and inward slope, renders the axle selfsteering as previously explained.

Figures 38, 39

This construction bears a superficial resemblance to that of Figs. 34, 35 but is actually quite with a Y shaped lever is pivoted at Ulsto the vehicle frame Ills. These connections carry all of the torque forces emanating-from the axle. Resilient resistance to movement of the lever 62s 65 is derived from a helical spring lilis which is interposed-between one side of the vehicle frame and an intermediate portion of a depressing lever I". The latter is pivoted at I50 to the vehicle frame and pivoted at ii! to thelower end of a relay link I" whose upper end ispivoted at It! to aforesaid Y lever 62s.. The depressing lever II! may be very light in construction as it only carries vertical loads and even these it is relieved of when theybecome too heavy, the various'link- 1g 

